I agree in some part with MasterQuest, step sparring is needed to practice some techniques and to develop muscle memory. I don't see how you will practice blocking a punch or countering with a kick, or even side steping kicks if you don't practice step sparring, step sparring helps you develop accuracy, speed, and timing. I don't agree that TKD is the best def against grappling, kicking sure is the first def but not the best, knowing how grappling works is.

Damn, one step. Well I always hated one step sparring, but my instructor was a little more hardcore about it. For the first half of my training one step was the tepid-paced unpractical lame stuff that you see in these videos. But as I advanced and got older, my instructor continued to increase its meaning by demanding speed, near full contact, and randomizing the attack. My older brother and I trained together primarily, and I can't count the number of times he has dropped me to the ground windless/knocked me silly in the head.
Anyhoo, I was usually always paired with him for one-step, and for higher level students he simply would not allow the lameness the 65 year old fat "black" belt was offering up. I think that one step has it's applications if trained first traditionally, then more practically once the student gets the basic movements down.
Lame wimpy crap like what is in those one-step videos makes me cry.

So did Josu just run around necroing threads in order to look retarded? The SOLE purpose that One step sparring was put to in my old TKD school was to introduce the kids to the idea of having another person in front of them trying to hit them. After low green belt (White, orange, yellow, low green) there were no more one steps for them. They padded up and sparred. I liked this idea because frequently the kids just spazzed out if they weren't used to something. And for the record I'm talking about 4-6 year olds.